These can be hardware, plugged in between the keyboard and the CPU, or software. And sometimes they're used for good, and not evil. I had someone using my home PC a few years ago. They erased the browser history files when they were done, so I installed a keylogger so I could see where they were going. It was not good. That person had "borrowed" a key from a family member to enter my home and do this.
Long story short, and focusing on the topic, not the scumbag, these can be used by management for monitoring but are more often associated with the theft of data and access means.
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AndyZ CRCM
My opinions are not necessarily my employers.
R+R-R=R+R
Rules and Regs minus Relationships equals Resentment and Rebellion. John Maxwell